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    <p><strong>tl;dr: Generic Pattern Counter</strong></p> <pre><code>// THIS IS WHAT YOU NEED const count = (str) =&gt; { const re = /YOUR_PATTERN_HERE/g return ((str || '').match(re) || []).length } </code></pre> <p>For those that arrived here looking for a generic way to count the number of occurrences of a regex pattern in a string, and don't want it to fail if there are zero occurrences, this code is what you need. Here's a demonstration:</p> <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false"> <div class="snippet-code"> <pre class="snippet-code-js lang-js prettyprint-override"><code>/* * Example */ const count = (str) =&gt; { const re = /[a-z]{3}/g return ((str || '').match(re) || []).length } const str1 = 'abc, def, ghi' const str2 = 'ABC, DEF, GHI' console.log(`'${str1}' has ${count(str1)} occurrences of pattern '/[a-z]{3}/g'`) console.log(`'${str2}' has ${count(str2)} occurrences of pattern '/[a-z]{3}/g'`)</code></pre> </div> </div> </p> <p><strong>Original Answer</strong></p> <p>The problem with your initial code is that you are missing the <a href="http://www.javascriptkit.com/jsref/regexp.shtml" rel="noreferrer">global identifier</a>:</p> <pre><code>&gt;&gt;&gt; 'hi there how are you'.match(/\s/g).length; 4 </code></pre> <p>Without the <code>g</code> part of the regex it will only match the first occurrence and stop there.</p> <p>Also note that your regex will count successive spaces twice:</p> <pre><code>&gt;&gt;&gt; 'hi there'.match(/\s/g).length; 2 </code></pre> <p>If that is not desirable, you could do this:</p> <pre><code>&gt;&gt;&gt; 'hi there'.match(/\s+/g).length; 1 </code></pre>
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    1. USPaolo Bergantino
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    1. COThis works as long as you have at least one space in your input. Otherwise, match() annoyingly returns null.
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    2. COsfink is right, you definitely want to check if match() returned null: `var result = text.match(/\s/g); return result ? result.length : 0;`
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      1. USGras Double
    3. COYou can also protect against the null by using this construction: `( str.match(...) || [] ).length`
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